The present invention relates generally to earth working implements and more particularly relates to a field cultivator shank for use on a tool bar of a field cultivator.
field cultivator shanks are typically pivotably mounted to a tool bar by a mounting bracket so as to permit the field cultivator shank to pivot upwardly and over an immovable object such as a rock. Generally, a coil spring is utilized to provide a downward bias to restore the field cultivator shank to an original orientation after the immovable object has been overcome. A need still exists, however, to provide a field cultivator shank assembly having an improved ability to withstand side load forces and having an improved ability to move out of the way of immovable objects. One way to improve the ability of the spring shank assembly to move out of the way of immovable objects is to improve the obstacle clearance height through which the shank may travel.
A need also exists for an improved field cultivator shank assembly wherein side bending load forces incurred by the downward biasing coil spring at the top of the coil spring during compression are either greatly decreased or eliminated.
A spring trip shank assembly is known in which a downwardly biasing coil spring acts to restore a shank to a desired position after an obstacle has been encountered in a manner such as is disclosed in U.S. Pat. No. 3,700,039 issued to Essex et al. A mounting element extends diagonally with respect to a tool bar with the spring being attached at one end to the mounting bracket and at another end to a clamp disposed on the shank. The coil spring acts against an upper end of the mounting bracket and is not pivotably connected to the mounting bracket. Furthermore, the clamping member is carried by the spring shank and is not pivotably connected to the mounting bracket.
A mechanism for adjusting a pre-load spring bias of the coil spring in a spring trip shank assembly is disclosed in U.S. Pat. No. 3,700,038 issued to Essex. A clamp member which is carried by the shank may be reversed so as to vary the moment arm through which the spring force acts and to accordingly vary the force needed to pivot the shank upwardly.
Another spring trip cultivator shank assembly is known and is disclosed in U.S. Pat. No. 3,981,367 issued to Mydels wherein a downwardly biasing coil spring is mounted somewhat similarly to that of the Essex patents discussed above. The coil spring is received at a lower end by a U-shaped spring guide member which is disposed above the spring shank. A leaf spring is provided between a lower end of the mounting bracket and the U-shaped spring guide member and serves to maintain the spring shank in a desired position with respect to the mounting bracket.
Numerous spring shank assemblies have been disclosed wherein the mounting bracket which is attached to the tool bar extends either vertically or forwardly with respect to the tool bar. Examples of such field cultivator shank assemblies are provided in the following U.S. Pat. Nos. 3,258,076 issued to Groenke; 3,480,086 issued to Groenke; 3,098,529 issued to Wade et al; and 3,493,055 issued to Van Peursem.
It is an object of the present invention to provide a field cultivator shank assembly wherein a quick dismounting of the spring assembly is provided by a pivotal mounting between the spring assembly and the mounting bracket.
Another object of the present invention is to provide a field cultivator shank wherein an upper spring abutting surface is provided above a pivot center line of an end casting or tube member of the spring assembly so as to minimize wear of the casting or tube member as a result of contact with the mounting bracket.
Still another object of the present invention is to provide a field cultivator shank wherein an attachment clamp which secures the mounting bracket to the tool bar is provided with angular fingers to place the ends of the attachment clamp in compression rather than tension when assembly bolts are tightened.
Yet still another object of the present invention is to provide a field cultivator shank wherein a preload compression of the coil spring may be adjusted.
Still yet another object of the present invention is to provide a field cultivator shank wherein the preload compression force of the coil spring may be selectively adjusted between first and second preload compression forces by means of a two position lever mechanism.
An earth working implement such as a field cultivator shank for use on a tool bar of a field cultivator according to the present invention includes a mounting bracket having an upper end and a lower end. The mounting bracket is secured to a tool bar at the lower end of the mounting bracket by an attachment member so that the upper end of the mounting bracket extends rearwardly and upwardly of the tool bar. A spring shank is pivotably connected to a lower end of the mounting bracket at a first pivot point with the spring shank extending rearwardly and downwardly of the lower end of the mounting bracket and terminating in a rounded end portion. The spring shank is securely engaged at an upper portion by a support bracket which is pivotably connected to the mounting bracket and terminates at a rearward end.
A coil spring which biases the spring shank downwardly and away from the upper end of the mounting bracket has a generally cylindrical configuration and is provided between the upper end of the mounting brackets and the rearward end of the support bracket. During compression of the coil spring, a generally cylindrical configuration is maintained by a spring guide member which also limits the downward travel of the spring shank and the support bracket. The coil spring is pivotably mounted at an upper end of the mounting bracket by a spring pivotal mounting member. The mounting bracket may be attached to the tool bar by an attachment clamp having first and second flange ends provided with first and second finger portions respectively. The first and second finger portions extend away from the attachment clamp towards the mounting bracket whereby the first and second flange portions are biased away from the mounting bracket. The pre-load compression of the coil spring may be selectively adjusted by a two position lever member provided between the coil spring and the support brackets.